This study is a follow-up to study "Energy Requirement and Energy Intake in Infants with Cyanotic Congenital Heart Disease." Which investigated the cause of growth failure in cyanotic congenital heart disease (CCHD). In the original protocol, a group of infants with cardiac defects was compared to a group of controls shortly after birth and again at three to four months of age by which time problems with growth failure was expected to have manifested. Resting metabolic rate was measured using respiratory calorimetry and both respiratory calorimetry and DLW assess energy expenditure by measuring CO2 production.